The present invention relates to a toolhead for chip-forming machine tools.
More specifically, the present invention relates to a toolhead of the type presenting an axis and comprising an outer casing; at least one sleeve coaxial with said axis and connected in axially-sliding, angularly-fixed manner to the casing; a tool spindle connected in rotary, axially-fixed manner to the sleeve; first drive means for rotating the spindle about said axis and in relation to the sleeve; and second drive means for moving the sleeve along said axis and in relation to the casing.
In known toolheads of the type described above, rotation of the spindle in relation to the sleeve and axial displacement of the sleeve in relation to the outer casing are achieved by means of a respective first and second motor located outside the sleeve and connected respectively to the spindle and sleeve via respective, e.g. gear or belt, drives and normally splined type couplings.
The location of the above motors and the presence of the drives connecting the motors to the respective driven elements render the above known toolheads not only cumbersome and complex in design but also relatively unreliable, especially by virtue of the large number of components in relative motion and, as such, subject to wear.
In order to overcome the above drawbacks, it is known from U.S. Pat. No. 5,009,554 and EP-A-0 362 781 to provide a toolhead of the type described above, in which the above first and second motors, the respective drives and the sleeve, which in EP-A-0 362 781 is integral with the aforementioned tool-carrying spindle, are all aligned with one another along the axis of the casing.
The above arrangement simplifies the design of the toolhead, reduces the number of components in relative motion, and increases reliability, but introduces a limitation in the rigidity of the spindle and, therefore, in the torque and shear which may be applied thereto. This is due to the fact that the spindle and the sleeve are to be mounted through at least one of the motors, and have limited diameters if costs and size are to be maintained within acceptable limits.